As one of light source devices used in a backlight of a liquid crystal display device, etc., a surface illuminant which comprises light emitting elements and light guide elements is known. Further, Patent Document 1 for instance discloses an art for enlarging a surface illuminant of this configuration. The art is that wedge shaped light guide elements are tandem arranged and each of the light guide elements is provided with a light emitting element such as a cold cathode fluorescent lamp. This art is illustrated in FIGS. 20 to 22.
As shown in FIG. 20, a light source device 101 has primary light sources (cold cathode fluorescent lamps) L1, L2 and first and second light guide blocks BL1, BL2. The first and second light guide blocks BL1, BL2 are tandem arranged in supply direction of the primary light. A double-faced prism sheet (not illustrated) is provided on emitting surfaces 115, 125 respectively. One end face of each light guide block BL1 and BL2 is referred to as a light entrance face 112 (122) from which primary light supplied from the primary light source L1 (L2) enters.
The light guide block BL1 (BL2) is reduced in thickness from the light entrance face 112 (122) to an apical end 117 (127). A recess is made hereby behind the apical end 117 of the light guide block BL1. The recess is used for providing the second primary light source L2 which supplies the primary light to the light guide block BL2. The first primary light source L1 is provided along the light entrance face 112.
As shown in FIG. 21, the tandem arranged light guide blocks BL1, BL2 the prime light sources L1, L2, and the prism sheets (not illustrated) are contained in a housing (case) 150 as an assembly. The housing 150 contains mounting sections for primary light sources 151, 152, and mounting sections for light guide blocks 153, 154 in a rectangular frame 155. The mounting sections for primary light sources 151, 152 have slopes corresponding with the slant of rear faces 116, 126 of the light guide blocks BL1, BL2. The slopes serve as reflection surface. Further, fixing claws 156 are provided on the inner walls E1, E2 (in tandem (y) direction) of the flame 155. The fixing claws 156 are used for fixedly holding the light guide blocks BL1, BL2 in the housing 150.
In the light source device, the light from the primary light source L1 enters into the light guide block BL1. The light, while being scattered and reflected, is guided to the apical end 117 toward which the light guide block BL1 becomes thinner. In this step, illumination light is gradually emitted from the emitting surface 115 preferentially in a diagonally forward direction. The light emitted diagonally forward is directionally corrected to a two-dimensionally frontward direction by the double-faced prism sheet. There is a reflective element between the first light guide block BL1 and the second primary light source L2 (not illustrated). The reflective element prevents a direct light supply from the primary light source L2 to the light guide block BL1.
[Patent Document 1] Japanese Unexamined Patent Application Publication, Tokukaihei, No. 11-288611 (published on Oct. 19, 1999)